Integrated circuit technology has been progressing rapidly to the point where integrated circuits incorporating millions of transistors are possible in such products as cell phones, televisions, and personal computers.
However, as more and more complex products are developed, even more rapid development of new technologies is required to reduce the size of individual transistors, memory units, and their connections, and to change the materials used in the manufacture of integrated circuits. For example, newer technologies have included decreasing the spacings of conductive lines below 0.13 um and changing the materials being used from conventional aluminum conductor with silicon dioxide dielectric layers (Al/SiO2) combinations to copper conductor with low or ultra-low dielectric constant material (Cu/low or ultra-low k) systems.
With the introduction of Cu/low or ultra-low k systems, reliability issues never seen before have occurred. For example, moisture attacks have occurred during package-level autoclaving, pressure cooker testing (PCT), thermal humidity bias (THB) testing, and highly accelerated stress test (HAST) testing.
It was found that micro-cracks were induced in the periphery of the integrated circuits during the wafer dicing process and that moisture could penetrate through the micro-cracks along the conductor and low k dielectric interface. This moisture penetration eventually leads to failures of the integrated circuits.
The moisture failure problems become more prominent when ultra-low k dielectric materials are used because such materials have extremely porous structures which are more vulnerable to moisture attack.
Other problems, which occur with the use of new materials and the move toward smaller integrated circuit line spacings, include delamination between the top dielectric layer containing the metal wires (intermetal dielectric layers (IMD)) and the capping layer, and copper out-diffusion after the delamination occurs.
Solutions to these problems have been long sought, but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.